medium CVSS 5.5 EPSS <0.1%

CVE-2024-36966·Kernel vulnerability

In the Linux kernel, the following vulnerability has been resolved: erofs: reliably distinguish block based and fscache mode When erofs_kill_sb() is called in block dev based mode, s_bdev may not have been initialised yet, and if CONFIG_EROFS_FS_ONDEMAND is enabled, it will be mistaken for fscache mode, and then attempt to free an anon_dev that has never been allocated, triggering the following warning: ============================================ ida_free called for id=0 which is not allocated. WARNING: CPU: 14 PID: 926 at lib/idr.c:525 ida_free+0x134/0x140 Modules linked in: CPU: 14 PID: 926 Comm: mount Not tainted 6.9.0-rc3-dirty #630 RIP: 0010:ida_free+0x134/0x140 Call Trace: <TASK> erofs_kill_sb+0x81/0x90 deactivate_locked_super+0x35/0x80 get_tree_bdev+0x136/0x1e0 vfs_get_tree+0x2c/0xf0 do_new_mount+0x190/0x2f0 [...] ============================================ Now when erofs_kill_sb() is called, erofs_sb_info must have been initialised, so use sbi->fsid to distinguish between the two modes.

Severity
medium
Software
Kernel
Fixed in
6.8.11
Published

How likely is exploitation

FIRST's Exploit Prediction Scoring System puts the probability of this CVE being exploited in the next 30 days at <0.1% — higher than 9% of all published CVEs. EPSS is an independent forecast of exploitation, not a severity rating: it says nothing about how much damage a successful attack does, which is what a CVSS score measures.

Affected versions

From: 6.7

Until: 6.8.11

Fixed in: 6.8.11

How to fix this CVE

Update your Linux kernel to version 6.8.11 or later to resolve a resource management flaw in EROFS filesystem handling. This vulnerability affects systems with CONFIG_EROFS_FS_ONDEMAND enabled, causing kernel warnings and potential instability during mount operations. Apply the latest kernel patches from your distribution's stable repository.

sudo dnf update kernel kernel-devel

Defensia detects this vulnerability

How to check if you are affected

  1. Step 1: Check your kernel version with 'uname -r' and compare against 6.8.11 — versions 6.7.x through 6.8.10 are vulnerable
  2. Step 2: Verify if EROFS filesystem is in use by checking 'mount | grep erofs' and 'grep CONFIG_EROFS_FS_ONDEMAND /boot/config-$(uname -r)'
  3. Step 3: Search kernel logs for 'ida_free called for id=0 which is not allocated' warnings using 'dmesg | grep ida_free' or 'journalctl -xe | grep ida_free'
  4. Step 4: After patching, run 'uname -r' to confirm the updated kernel version is active (may require reboot) and remount EROFS filesystems to verify stability

FAQ

What is CVE-2024-36966?

This vulnerability exists in the Linux kernel's EROFS filesystem implementation where the shutdown routine (erofs_kill_sb) incorrectly distinguishes between block-device and fscache modes when CONFIG_EROFS_FS_ONDEMAND is enabled, leading to attempts to free unallocated device IDs and generating kernel warnings.

Is CVE-2024-36966 being actively exploited?

No — this CVE is not listed on CISA's Known Exploited Vulnerabilities catalog and no public exploits are available. However, it can cause system instability and kernel warnings during normal EROFS mount operations.

What versions of Kernel are affected by CVE-2024-36966?

Linux kernel versions 6.7.0 through 6.8.10 are affected. Version 6.8.11 and later contain the fix. Systems running kernels outside this range are not vulnerable.

How do I check if my server is vulnerable to CVE-2024-36966?

Run 'uname -r' and verify the version is between 6.7 and 6.8.10. Then check 'grep CONFIG_EROFS_FS_ONDEMAND /boot/config-$(uname -r)' — if it shows 'y', your system is vulnerable only if using EROFS filesystems.

Does Defensia detect CVE-2024-36966?

Yes — Defensia's CVE advisory scanner compares installed kernel versions against the NVD database. If a vulnerable kernel version is detected on a monitored server, CVE-2024-36966 will appear in your dashboard with automated remediation guidance and patch availability.

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References

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